1. Field of the Invention
The present invention relates to methods and systems for producing crude oil from a reservoir of heavy oil or bitumen by steam-assisted gravity drainage (SAGD) processes. More particularly, the present invention relates to the injection, for production and gather systems, of field wells by using basic block units as a building block that could be installed with minimal cost and minimal on-site labor. More particularly, the present invention relates to modular systems that can be employed in such SAGD processes.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
Heavy oil reservoirs contain crude petroleum having a API gravity less than about 10 which is unable to flow from the reservoir by normal natural drive primary recovery methods. These reservoirs are quite difficult to produce. The tar sand deposits in Canada are typically heavy oil deposits that cannot be produced by standard technology. The steam-assisted gravity drainage (SAGD) process is commonly used to produce heavy oil and bitumen reservoirs. This generally includes the injection of steam, sometimes with a solvent, into an upper horizontal well through the reservoir to generate a steam that heats the petroleum to reduce the viscosity and make it flowable. Production of the heavy oil or bitumen is from a lower horizontal well through the reservoir disposed below the upper horizontal well. The SAGD and its further developing technology requires a significant amount of equipment. This equipment includes piping, valves, insulation, tracing, and electric instrumentation that is concentrated at the location of the well. Another typical characteristic of the SAGD is the close proximately of the injection and the production wells. A group of injection and production wells are gathered together on a certain location to produce a certain underground deposit. This complex of wells is typically defined as a pad.
The SAGD development over the years has concentrated on the process itself and especially on the underground portion of the process. However, because of the locations and the general conditions, especially in Alberta oil sands, the cost of the constructed facility and the scheduling risk are playing an increasing role.
The heavy oil or bitumen produced by the SAGD and similar methods require large amounts of steam generated and injected to the oil sand deposit. The heavy oil or bitumen has a very high viscosity that makes it difficult to transport and store. It must be kept at an elevated temperature and/or is sometimes mixed with a lighter hydrocarbon diluent for pipeline transportation. Because of this, the production wells is complex and contains a significant amount of insulated and heat-traced pipes, control valves and equipment which must be maintained in close proximity to the well heads.
In the past, SAGD oil field were built using the traditional approach of field construction. The flow lines connecting the well heads were connected to the equipment in the field. It is also a common practice to install most of the equipment on skids or modules and to install and connect those units between the wellheads and the flow lines.
The use of platforms in the offshore industry is well known. In the offshore industry, there is a significant importance for the ease of the construction and the method of the construction. An additional factor is that, on an offshore platform, everything must be pre-fabricated in a remote location. For example, U.S. Pat. No. 5,775,846 describes an offshore production platform and method of installing such a platform. U.S. Pat. No. 5,505,151 describes a vessel structure that integrated independent modular units for oil production at sea. The only similarity with the off-shore prior art is the fact that in the offshore cases, the constructed complex, along with the manner in which it is constructed, is a significant economic factor in project planning. As such, oil production is not the only item that drives the economics and feasibility of the oil production project and there is a significant importance to the systems and methods used to construct an off shore projects.
There is an unmet need in the art for a way to reduce the cost of SAGD construction. There is also a need to reduce scheduling risks due to uncontrolled field conditions. It is important to be able to minimize these costs by providing a solution that allows construction to be carried out using a standard basic platform unit that is pre-assembled. These units can be connected to each other so as to build most of the oil production pad, including its pipes and flow lines.
The current SAGD technology typically constructs pads with field constructed flow lines, electrical cables trays and piping. The pipes are connected to the well heads using modules that contain valves, control equipment, electrical equipment and instrumentation. All the connection between the equipment modules to the flow lines is done in the field. A major disadvantage in the manner in which SAGD is currently constructed is the need for significant amount labor to be carried out in the field. This is subjected to high labor costs, environment impacts, and scheduling risks. It is important to minimize and simplify these disadvantages by standardizing work in the shops and the work in the field by producing a standard unit that will includes the flow lines, the piping as well as the equipment all connected together on a transferable platform for the construction of the SAGD.
It is an object of the present invention to provide a system that avoids the need to separately construct and connect pipes in the field.
It is another object of the present invention to provide an assembly that can be easily transported to the desired location.
It is still a further object of the present invention to provide a system for SAGD that can be manufactured off-site.
It is another object of the present invention to provide a system for SAGD which minimizes the costs.
It is still a further object of the present invention to provide a system for SAGD which allows for a shorter construction schedule.
It is a further object of the present invention to provide a system for SAGD that minimizes hydro-testing requirements in the field.
It is still another object of the present invention to provide a system for SAGD that allows for the relocation of equipment after the well is depleted.
It is still a further object of the present invention to provide a system which improves safety for those involved with the assembly, manufacturer and production.
These and other objects and advantages of the present invention will become apparent from the reading of the attached specification and appended claims.